Using BMSC-derived Bone-Ligament-Bone Tissue as a Live Template for ACL Regenerat

描述（由申请人提供）：每年大约有35万例前交叉韧带（ACL）重建手术，并且在该手术中涉及的急性护理费用上花费了数十亿美元。最常见的前交叉韧带置换策略包括移植物（来自尸体的同种异体移植物或患者自己的髌骨或腿筋的自体移植物），尽管更新的、更多实验性的治疗方法使用工程组织，通常包括在聚合物支架上播种细胞。在这些手术中，移植物或工程组织无法与手术中形成的骨隧道完全融合，关节也无法恢复手术前的生物力学水平。不出所料，超过一半的接受过这种手术的患者会患上早发性骨关节炎（OA）。随着急性前交叉韧带损伤在儿童中越来越普遍，年轻成人患OA的人数每年都在增加。Larkin和Arruda实验室在过去的几年里一直在设计一种由骨髓来源的基质细胞（BMSCs）产生的ACL替代结构，该结构在体内移植时显示出天然ACL的结构和功能界面特征。该结构由两端具有工程骨的工程韧带组成；它完全融入受体骨，并在体内分化，在两个组织之间形成机械上适当和生物上匹配的界面。这些实验室的工作证明了该策略的许多优点，并且在大型动物模型中的证据支持其替代疗法的优越性。然而，在人类中使用这种新颖的创新疗法的一个关键问题是在患者中使用干细胞/前体细胞来源组织的安全性。必须证明用于生成这些构建体的骨髓间充质干细胞在移植后不会造成长期威胁。该领域主要关注的问题是确定没有未分化细胞持续存在的能力

DESCRIPTION (provided by applicant): Approximately 350,000 anterior cruciate ligament (ACL) reconstruction surgeries are performed each year, and billions of dollars are spent on the acute care costs involved in this procedure. The most common ACL replacement strategies involve grafts (allografts from cadavers or autografts of the patients' own patellar or hamstring tendons), although newer, more experimental treatments use engineered tissues that typically involve seeding cells on a polymeric scaffold. In these procedures, the graft or engineered tissue never fully integrates with the bone tunnel created during surgery and the joint never recovers pre-surgical level biomechanics. Not surprisingly, more than half of the patients who have undergone this procedure develop early-onset osteoarthritis (OA). With acute ACL injuries becoming increasingly prevalent in children, the number of young adults developing OA is increasing each year. The Larkin and Arruda laboratories have spent the last several years engineering an ACL replacement construct generated from bone marrow-derived stromal cells (BMSCs) that exhibits the structural and functional interface characteristics of native ACL when transplanted in vivo. The construct is composed of an engineered ligament with engineered bone at each end; it fully integrates into the recipient bone and differentiates in vivo to form a mechanically appropriate and biologically matched interface between the two tissues. Work from these laboratories demonstrates many advantages to this strategy and evidence in a large animal model supports its superiority for replacement therapy. One critical concern regarding the use of this novel and innovative therapy in humans, however, is the safety of use of stem/precursor cell-derived tissue in patients. It is imperative to demonstrate that the BMSCs used for the generation of these constructs pose no long-term threat after transplantation. The main concern in the field is the ability to ascertain that no undifferentiated cells persist in the transplanted construct that might later lead to aberrant cellular behavior such as cancer. In collaboration with Dr. Wellik's laboratory, a recent examination of the fate of the BMSC-derived BLB construct led to the surprising discovery that within several months after implantation of the BLB, donor construct cells are replaced entirely by recipient cells and donor-derived cells are no longer present. Thus, by transplanting a developmentally immature, exogenous live tissue template for replacement, adult recipient cells are induced to fully regenerate a viable and mechanically appropriate replacement ligament! This proposal seeks to confirm these preliminary results and initiate exploration into the mechanisms of this remarkable regenerative process, with the longer-term goal of translating this innovative therapy into humans and vastly improving the outcomes of acute ACL and potentially other joint and connective tissue injuries.